With the recent trend toward improvements in luminous efficiency and luminous flux and increase in current density in light-emitting diodes (LEDs), the deterioration of LED encapsulation resins has become a problem because it is causative of LED life shortening. In general, epoxy resins are frequently used as LED encapsulation resins. However, it is known that the enhanced heat generation due to the increase in injection current density further accelerates the deterioration of the epoxy resins.
Specifically, examples of the resins for use in the encapsulation of optical semiconductor elements include an alicyclic epoxy resin (see, JP-A-7-309927) and a polyimide-containing resin obtained by reacting an aromatic acid dianhydride with an aromatic diamine compound (see, JP-A-63-7657).
However, alicyclic epoxy resins still have insufficient heat resistance, while polyimide-containing resins obtained by reacting an aromatic acid dianhydride with an aromatic diamine compound are not sufficient in heat resistance and light-transmitting properties.